Blood pressure readings have two numbers, for example 140/90mmHg.
The top number is your systolic blood pressure. (The highest pressure when your heart beats and pushes the blood round your body.) The bottom one is your diastolic blood pressure. (The lowest pressure when your heart relaxes between beats.)
The blood pressure chart below shows ranges of high, low and healthy blood pressure readings.
Using this blood pressure chart: To work out what your blood pressure readings mean, just find your top number (systolic) on the left side of the blood pressure chart and read across, and your bottom number (diastolic) on the bottom of the blood pressure chart. Where the two meet is your blood pressure.
As you can see from the blood pressure chart, only one of the numbers has to be higher or lower than it should be to count as either high blood pressure or low blood pressure:
90 over 60 (90/60) or less: You may have low blood pressure.
More than 90 over 60 (90/60) and less than 120 over 80 (120/80): Your blood pressure reading is ideal and healthy.
More than 120 over 80 and less than 140 over 90 (120/80-140/90): You have a normal blood pressure reading but it is a little higher than it should be, and you should try to lower it.
140 over 90 (140/90) or higher (over a number of weeks): You may have high blood pressure (hypertension). see your doctor or nurse and take any medicines they may give you.